The invention relates to a method for the production of extruded plastic products using an extruder which has an extruder hopper which is supplied with a hot mixture obtained by discontinuous mixing of PVC powder and additives in a hot mixing zone, with the supply of frictional heat.
A method of this type is known EP-A-0 008 712. In this method the additives become predominantly soft or fluid at the elevated temperatures, as a consequence of frictional heat, as a result of which the said additives adhere very well to the PVC powder.
Following the preparation of this mixture by discontinuous hot mixing, the mixture obtained is transferred into a horizontal rotating and homogenising heat-retaining silo, from which the extruder is fed continuously or discontinuously. With this method the additives can be supplied to the mixer from a central weighing installation.
One drawback of this method is that a horizontal heat-retaining silo is needed in the extrusion line, while, moreover, a great deal of space is lost because a high vertical mixing installation is positioned above each extruder, as a result of which the building costs for a factory are appreciably increased.